As the documentation also notes, manufacturers can provided decoders for additional media formats, meaning that this can potentially vary by device a bit. I'm not aware of any simple way to determine which extra formats are supported by a device aside from simply copying a sample over and attempting to play it with the stock music player.

The MOTODEV Site has the internal specs for every Motorola Android device. If you scroll to the "Media" section, you'll see the list of supported formats. Usually it's the Core Media Formats plus any extras.